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Final Observations  Must defend against following spoofing strategy: (1) soften up target with low-grade jamming, (2) begin soft- estimate replay attack, (3) transition to hard-estimate replay attack  A J/N meter is indispensable in spoofing detection to eliminate the possibility that the receiver’s estimate of its own nominal C/No (in the absence of spoofing) has been altered  Solar radio bursts, unintentional/intentional jamming will tend to trigger spoofing alarms  Spoofing detection is challenging for dynamic platforms because of the volatility in the nominal C/No